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Operation
Nodepool has two components which run as daemons. The
nodepool-builder daemon is responsible for building
diskimages and uploading them to providers, and the
nodepoold daemon is responsible for launching and deleting
nodes.
Both daemons frequently re-read their configuration file after starting to support adding or removing new images and providers, or otherwise altering the configuration.
Nodepool-builder
The nodepool-builder daemon builds and uploads images to
providers. It may be run on the same or a separate host as the main
nodepool daemon. Multiple instances of nodepool-builder may
be run on the same or separate hosts in order to speed up image builds
across many machines, or supply high-availability or redundancy.
However, since nodepool-builder allows specification of the
number of both build and upload threads, it is usually not advantageous
to run more than a single instance on one machine. Note that while
diskimage-builder (which is responsible for building the underlying
images) generally supports executing multiple builds on a single machine
simultaneously, some of the elements it uses may not. To be safe, it is
recommended to run a single instance of nodepool-builder on
a machine, and configure that instance to run only a single build thread
(the default).
Nodepoold
The main nodepool daemon is named nodepoold and is
responsible for launching instances from the images created and uploaded
by nodepool-builder.
When a new image is created and uploaded, nodepoold will
immediately start using it when launching nodes (Nodepool always uses
the most recent image for a given provider in the ready
state). Nodepool will delete images if they are not the most recent or
second most recent ready images. In other words, Nodepool
will always make sure that in addition to the current image, it keeps
the previous image around. This way if you find that a newly created
image is problematic, you may simply delete it and Nodepool will revert
to using the previous image.
Daemon usage
To start the main Nodepool daemon, run nodepoold:
nodepoold --help
To start the nodepool-builder daemon, run nodepool--builder:
nodepool-builder --help
To stop a daemon, send SIGINT to the process.
When yappi (Yet Another Python Profiler) is available, additional functions' and threads' stats are emitted as well. The first SIGUSR2 will enable yappi, on the second SIGUSR2 it dumps the information collected, resets all yappi state and stops profiling. This is to minimize the impact of yappi on a running system.
Metadata
When Nodepool creates instances, it will assign the following nova metadata:
- groups
A comma separated list containing the name of the image and the name of the provider. This may be used by the Ansible OpenStack inventory plugin.
- nodepool_image_name
The name of the image as a string.
- nodepool_provider_name
The name of the provider as a string.
- nodepool_node_id
The nodepool id of the node as an integer.
Command Line Tools
Usage
The general options that apply to all subcommands are:
nodepool --help
The following subcommands deal with nodepool images:
dib-image-list
nodepool dib-image-list --help
image-list
nodepool image-list --help
image-build
nodepool image-build --help
dib-image-delete
nodepool dib-image-delete --help
image-delete
nodepool image-delete --help
The following subcommands deal with nodepool nodes:
list
nodepool list --help
hold
nodepool hold --help
delete
nodepool delete --help
If Nodepool's database gets out of sync with reality, the following commands can help identify compute instances or images that are unknown to Nodepool:
alien-list
nodepool alien-list --help
alien-image-list
nodepool alien-image-list --help
In the case that a job is randomly failing for an unknown cause, it
may be necessary to instruct nodepool to automatically hold a node on
which that job has failed. To do so, use the the job-create
command to specify the job name and how many failed nodes should be
held. When debugging is complete, use ''job-delete'' to disable the
feature.
job-create
nodepool job-create --help
job-list
nodepool job-list --help
job-delete
nodepool job-delete --help
Removing a Provider
To remove a provider, remove all of the images from that provider`s configuration (and remove all instances of that provider from any labels) and set that provider's max-servers to -1. This will instruct Nodepool to delete any images uploaded to that provider, not upload any new ones, and stop booting new nodes on the provider. You can then let the nodes go through their normal lifecycle. Once all nodes have been deleted you remove the config from nodepool for that provider entirely (though leaving it in this state is effectively the same and makes it easy to turn the provider back on).
If urgency is required you can delete the nodes directly instead of waiting for them to go through their normal lifecycle but the effect is the same.